CycloDS Evolution. It has the most features like Slow-Mo, RTS and lots more. It also has one of the nicest GUI's and the best support. I got one last Monday and it's awesome! It's 50$. I would buy that.
Ok sure there is the Acekard 2.1, IMO is the second best. It doesn't have as much features as the Cyclo, but it is very good too. It's 30$ (I think).
Oh yeah, If you want a slot-2 device, get SuperCard. Or if you are going to get a Cyclo, you could get the EZ Flash 3 in 1 with it.
Don't get an R4, R4 Clone, DSTT and some others I can't remember.